A large numer of different devices have been proposed heretofore for agitating fluids within a test tube. The devices proposed heretofore are ineffective to provide for the breakage of bacterial cells with fine glass beads. The device disclosed in U.S. Pat. No. 4,118,801 is representative of prior art designed only to mix fluid contents in a plurality of vessels. There is a need for simple and efficient devices for breaking bacterial cells with beads while allowing for the cells to be cooled in a simple and inexpensive manner so as to prevent the destruction of proteins and enzymes released during cell breakage. None of the prior art known to me is capable of performing in that manner.